In less than one year the 1918 Spanish flu pandemic claimed over 20 million lives worldwide, killing 675,000 Americans, more than 10 times the number of deaths to US servicemen in World War I. A similar strain of the virus that caused the 1918 pandemic could today kill 2 million Americans and force 10 million to be hospitalized. Although anti-viral drugs are key to reducing the potentially deadly impact of a pandemic strain, influenza virus develops resistance to popular flu drugs such as oseltamivir (Tamiflu). Thus, a sensitive and robust assessment of the drug susceptibility of the virus must be available in the clinic to guide the most effective treatment of patients. However, established methods for the determination of virus infectivity, such as the plaque assay, lack sensitivity and are both time consuming and labor intensive to implement. This NIAID Advanced Technology STTR (Phase I) project between BellBrook Labs (Madison, Wisconsin), a small business specializing in cell-based tools for high throughput screening, and experts in virology and microfluidics at the University of Wisconsin-Madison is to develop a better method to measure the infectivity of viruses. We build on our observation that microscale fluid flows can enhance the spread of viruses in culture, producing measures of infection that are 10-to-100 fold more sensitive than the plaque assay and easier to perform. A US patent based on this idea has been filed. Specific aims of our two-year project will be to: (1) demonstrate flow-enhanced measurement of drug susceptibility of influenza virus, (2) implement the influenza infection assay in a micro-fluidic channel, and (3) assess the feasibility of a high-throughput infection assay. This research will set the foundation for a highly sensitive, high-throughput infection assay for influenza and other viruses of human medical importance. NARRATIVE Sensitive and robust assessments of the drug susceptibility of influenza virus must be available in the clinic to guide the most effective treatment of infected patients. However, established methods for the determination of virus infectivity lack sensitivity and are both time consuming and labor intensive to implement. This NIAID Advanced Technology STTR project combines emerging methods of microfluidics, quantitative imaging, and high-throughput processing to better measure virus infectivity. This research will set the foundation for a highly sensitive, high-throughput infection assay for influenza and other viruses of human medical importance.